Heat shield fastening structure for drum type washing machine with laundry drying function

ABSTRACT

Provided is a drum type washing machine combined with a dryer and employing an improved air passage structure that can enhance the drying efficiency and drying performance, in particular, that can prevent a tub from being deformed due to heat of a heater of the drying duct. The washing machine includes: a cylindrical plastic tub having a hot air inlet formed at a front upper portion thereof and a hot air outlet formed at a rear lower portion thereof; a drum rotatably installed inside the tub; a drying duct provided with a heater and a blower fan that are mounted on an inner air passage of the drying duct and fixed to an upper predetermined portion of an outer circumference of the tub; a condensation duct for removing moisture contained in hot air exhausted through the hot air outlet of the tub; and a heat shield interposed between the tub and the drying duct, for shielding heat of the drying duct from being transferred directly to the tub.

This application claims the benefit of the Korean Application No. P2004-26740 filed on Apr. 19, 2004, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a drum type washing machine, and more particularly, to a drum type washing machine combined with a dryer and employing a new air passage structure that can enhance the drying efficiency and drying performance.

2. Discussion of the Related Art

In general, the drum type washing machine washes laundry by using friction between a drum rotated by a driving force of a motor and laundry under a state detergent, washing water, and the laundry are received in the drum. The drum type washing machine has advantages in that the laundry is almost not involved in damage and tangling between the laundries, and in that washing effects obtainable by beating and rubbing the laundry can be provided.

A related art drum type washing machine will be explained with reference to FIG. 1.

FIG. 1 is a schematic side sectional view of a related art drum type washing machine.

Referring to FIG. 1, the washing machine includes a cabinet 1 having a laundry entrance formed at a front thereof, a door openably and closably installed at the laundry entrance of the cabinet 1, a metallic tub 3 disposed inside the cabinet 1, for storing washing water, a drum 9 rotatably installed inside the tub 3, and a motor unit 5 installed in the tub 3, for transferring a driving force to the drum 4.

The door 2 is provided with a door glass 2 a protruded toward an opening of the tub 3.

A hanging spring 6 for supporting the tub 2 is installed between an inner upper surface of the cabinet 1 and an upper outer circumferential surface of the tub 3. Although not shown in the drawing, a damper (not shown) for damping vibration of the tub 3 generating while the drum-type washing machine operates is installed between an inner lower surface of the cabinet 1 and a lower outer circumferential surface of the tub 3.

Also, the motor unit 5 mainly employs an indirect driving way in which the driving force generated by a motor 5 a is transferred to a washing shaft 5 c by a belt 5 c to thereby rotate the drum 4.

Meanwhile, a drying duct 7 is installed at an inner upper surface of the cabinet 1. The drying duct 7 is provided therein with a heater 7 b and a blower fan 7 a to generate hot air and forcibly blow the generated hot air.

One end of the drying duct 7 is connected to a gasket 8 connecting a front opening edge of the tub 3 with a surrounding portion of the door 2 of a front side of the cabinet 1.

In other words, the gasket 8 is installed along a front inner edge of the tub and has a bellows shape to receive the vibration of the tub 3. Accordingly, it can be prevented that hot air is leaked through a connection portion between the drying duct 7 and the tub 3.

Also, a condensation duct 9 communicating with the drying duct 7 is formed at the tub 3. One end of the condensation duct 9 is connected to an outer surface of the tub 3 and the other end of the condensation duct 9 is connected to the drying duct 7. A water feeder 9 a for feeding cooling water is installed at the condensation duct 9 such that moisture contained in air is condensed and removed.

The drum type washing machine constructed as above performs washing, rinsing, dehydration and drying cycles.

The drying cycle will now be described with reference to the accompanying drawings.

As the drying cycle of the drum type washing machine starts, a power is applied to the heater 7 b of the drying duct 7 to operate the blower fan 7 a and the heater 7 b. Accordingly, the blower fan 7 a blows hot air.

The hot air is guided by the drying duct 7 to collide with an inclined portion of the door glass 2 a and is then introduced into an inside of the drum 4.

The hot air introduced into the drum 4 heats laundry to vaporize the moisture contained in the laundry. At this time, the drum 4 rotates at a low speed to agitate the laundry and help the evaporation of the moisture such that the laundry is uniformly exposed to the hot air.

The vaporized moisture is discharged through the condensation duct 9 together with the air. At this time, the water feeder 9 a of the condensation duct 9 injects water to remove the moisture contained in the air. The moisture-removed air is again introduced into the drying duct 7, is converted into the hot air by the heater 7 b and the blower fan 7 a, and the converted hot air is again introduced into the drum 4 to perform the drying of the laundry.

By repeating the aforementioned operations, the laundry is dried.

However, in the related art drum type washing machine, since the drying duct is connected to an upper predetermined portion of the gasket, dry air is fed to the inside of the drum through the predetermined portion of the gasket and then discharged through a front side portion of the tub for the air circulation. Due to the above construction, the related art drum type washing machine has various problems, for example, the drying efficiency and the drying performance are limited.

First, since the air fed to the inside of the drum is discharged through a front side of the tub under the circumstance that the air is not penetrated to a deep place of the drum, the laundry positioned at the deep place of the drum is not sufficiently dried.

To this end, the related art air passage structure deteriorates the drying efficiency and the drying performance.

Next, in the related art drum type washing machine combined with a dryer, the drying duct is connected to the gasket. Then, since the drying duct is in a fixed state and the gasket is shaken while the tub vibrates, the gasket may be worn or torn, which is disadvantageous.

Owing to the above reason, the high price gasket 8 having a low heat deformation property should be installed, which increases the manufacturing cost.

In addition, the drying duct 7 is extended toward a vertical downward direction through the gasket, which is misaligned with the axial direction of the drum. To this end, since the discharged hot air collides with the door glass to be subject to resistance, it is problematic that the hot air does not reach a deep position of the drum.

To overcome the above problem, it is required to install a blower having a larger capacitance ever before.

Also, since the hot air of the drying duct 7 is via the gasket 8, is bent at the inclined portion of the door glass 2 a and is then introduced into the drum 4, the door 2 is unnecessarily heated.

Meanwhile, since the drying duct 7 is connected to the upper outer circumferential surface of the gasket 8, the upper portion of the gasket 8 is asymmetric to the lower portion of the gasket 8 and accordingly the gasket 8 does not balance the tub in the whole.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a drum type washing machine combined with a dryer that substantially obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a drum type washing machine combined with a dryer and employing an improved air passage structure that can enhance the drying efficiency and drying performance, in particular, that can prevent a tub from being deformed due to heat of a heater of the drying duct.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a washing machine including: a cylindrical plastic tub having a hot air inlet formed at a front upper portion thereof and a hot air outlet formed at a rear lower portion thereof; a drum rotatably installed inside the tub; a drying duct provided with a heater and a blower fan that are mounted on an inner air passage of the drying duct and fixed to an upper predetermined portion of an outer circumference of the tub; a condensation duct for removing moisture contained in hot air exhausted through the hot air outlet of the tub; and a heat shield interposed between the tub and the drying duct, for shielding heat of the drying duct from being transferred directly to the tub.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:

FIG. 1 is a schematic side sectional view of a related art drum type washing machine;

FIG. 2 is schematic side sectional view of a drum type washing machine according to the present invention;

FIG. 3 is an exploded perspective view of a main part of FIG. 2;

FIG. 4 is a schematic plane view of a heat shield according to the present invention and shows an installation state of the heat shield to a tub;

FIG. 5 is a sectional view of a main part in a heat shield fastening structure according to the present invention; and

FIG. 6 is a plane view of a heat shield according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

FIG. 2 is schematic side sectional view of a drum type washing machine according to the present invention, FIG. 3 is an exploded perspective view of a main part of FIG. 2, FIG. 4 is a schematic plane view of a heat shield according to the present invention and shows an installation state of the heat shield to a tub, and FIG. 5 is a sectional view of a main part in a heat shield fastening structure according to the present invention.

Referring to FIGS. 2 through 5, the washing machine includes a tub 20 installed inside a cabinet 10 to store washing water, and having a hot air inlet 20 a formed at a front upper portion thereof and a hot air outlet 20 b formed at a rear lower portion thereof, a drum 30 rotatably installed inside the tub 20 and having a plurality of hot air passing holes 30 a formed at a front side thereof with a predetermined configuration, a drying duct 40 fixedly installed on an upper outer circumferential surface of the tub 20, provided therein with a heater 41 and a blower fan 42 so as to generate hot air, of which one end is connected to the hot air inlet 20 a of the tub 20 to feed the hot air generated therein to an inside of the drum 30, a condensation duct 50 installed at a rear of the tub 20 such that one end thereof is connected to the hot air outlet 20 b of the tub 20 and the other end is connected to the drying duct 40, for removing moisture contained in the hot air exhausted from the tub 20 to feed the moisture-removed air to the dying duct 40, and a heat shield 43 interposed between the tub 20 and the drying duct 40, for shielding heat of the drying duct 40 from being transferred directly to the tub 20.

Preferably, the heat shied 40 is made of metal material such as an iron plate, but it may be made of plastic material that is not deformed by heat.

The heat shield 43 includes a base portion 43 a being closely in contact with the tub 20, and an embossing portion 43 b spaced apart from an outer surface of the tub 20 by a predetermined interval, to which the drying duct 40 is fixed. A duct-screwing hole 432 is formed at a center portion of the embossing portion 43 b of the heat shield 43 to screw the drying duct 40 to the heat shield 43 using a screwing piece 410 provided in the drying duct 40, and a plate-screwing hole 431 is formed at both edges of the embossing portion 43 b to screw the heat shield 43 to the tub 20.

Referring to FIGS. 3 and 4, the embossing portion 43 b are formed in plurality in the form of a band, and includes two embossing portions formed at a position facing each other in a circumferential direction, and the other(s) embossing portion formed at a position spaced apart from the two embossing portions by a predetermined distance in an axial direction of the tub.

In addition, the duct-screwing holes 432 formed at the respective center portions of the two embossing portions facing each other are formed at different positions.

Meanwhile, in the present embodiment having the two embossing portions 43 b formed at a position facing each other in a circumferential direction, the plate-screwing hole 431 and the duct-screwing hole 432 are formed at the same time. In addition, a two-stage embossing portion 43 c is formed around the plate-screwing holes 431 formed at both end portions of the two embossing portions 43 b and is twice embossed to make it easy to determine an assembling position between the heat shield 43 and a coupling boss 200 formed at the tub 20.

Also, at the other(s) embossing portion formed at a position spaced apart from the two embossing portions by a predetermined distance in an axial direction of the tub, only the duct-screwing hole is formed. And, a plate-screwing hole is separately formed at an embossed portion adjacent thereto.

The screwing piece 410 formed in the drying duct 40 has a length protruded downward than a lower surface of the drying duct 40.

Also, the heat shield is configured to have an area covering a transferable range of radiant heat from the heater of the drying duct 40.

Meanwhile, the hot air passing holes 30 a formed in the drum 30 have a radial configuration.

The drum 30 is preferably rotated in a direct driving way by an outer rotor type BLDC motor, which includes a shaft 61 penetrating the tub 20 and axially connected to the drum 30, a rotor 62 coupled to a rear end of the shaft 61, and a stator 63 positioned inside the rotor 62, but is not necessarily limited thereto.

In addition, a radiation mechanism such as a radiation fin 44 may be formed on the drying duct 40. The radiation mechanism increases the radiation area to prevent the upper surface of the drying duct 40 from being overheated.

Operation of the above-described drum type washing machine with drying function will now be described.

First, the hot air inlet 20 a and the hot air outlet 20 b are designed such that the hot air inlet 20 a is formed at the front upper portion of the tub 20 and the hot air outlet 20 b is formed at the rear lower portion of the tub 20.

By doing so, the inflow direction of the hot air into the inside of the drum 30 and the outflow direction of the hot air to the condensation duct 50 are arranged to form a diagonal line. Accordingly, the hot air uniformly reaches even a deep place of the inside of the drum 30 to uniformly dry the laundry and is then discharged.

Next, the hot air inlet 20 a of the tub 20 is formed at the front upper portion of the tub 20 and the hot air passing holes 30 a are arranged forming a concentric circle on a front surface of the drum 30. Also, the hot air passing holes 30 a are arranged forming a straight line in a radial direction of each column or are arranged forming a zigzag configuration.

In other words, the hot air passing holes 30 a formed at the front side of the drum 30 are formed, not lowering the strength of the front side of the drum 30 and having a maximum sectional area of the air passage.

Thus, the hot air passing holes 30 a are formed in an effective configuration throughout the whole front surface of the drum 30. To this end, even though the drum 30 rotates, since the hot air inlet 20 a communicates with the hot air passing holes 30 a, the hot air inflowing into the inside of the tub 20 through the hot air inlet 20 a can be smoothly fed to the inside of the drum 30 through the hot air passing holes 30 a formed at the front surface of the drum 30.

Meanwhile, the heat shield 43 is disposed below the drying duct 40 to prevent the hot air generated in the drying duct 40 from being transferred to the tub 20.

In other words, if the plastic drying duct provided therein with the heater is fixed direct to the tub 20, the drying duct may be deformed due to the heat of the heater. To this end, the heat shield 43 that is a separate member first shields the heat of the drying duct side from being transferred directly to the tub 20.

In addition, due to the existence of the heat shield 43, since the heat transferred to the heat shield 43 through the screwing piece 410 of the drying duct 40 and a screw ‘S’ screwed to the screwing piece 410 may be again directly transferred to the tub 20, the screwing portion of the drying duct screwing piece 410 on the heat shield 43 is embossed such that the outer circumference of the tub 20 is spaced apart from the heat shield 43, thereby secondly shielding the heat of the drying duct side from being transferred directly to the tub 20.

For this purpose, the heat shield 43 is first fixedly screwed to the outer surface of the tub 20 and the drying duct 40 is fixedly screwed to the embossing portion 43 b on the heat shield 43 by a screwing member such as a screw ‘S’ under the circumstance that the heat shield 43 is fixed to the tub 2.

At this time, it is preferable that the embossing portion 43 b formed on the heat shield 43 is formed having a sufficient height and the screw for screwing the drying duct 40 to the heat shield 43 is also spaced apart from the tub 20.

Meanwhile, if the embossing portion 43 b of the heat shield 43 is not sufficiently high, the screw for screwing the drying duct 40 to the heat shield 43 contacts the tub 20, which is disadvantageous because heat is directly transferred to the tub 20 through the screw.

Meanwhile, the heat shield 43 is designed to have a sufficient area capable of covering a transferable range of radiant heat generated from the heater of the drying duct 40.

In summary, in the present invention, the drying duct 40 is not directly coupled to the plastic tub 20 but is indirectly coupled to the embossing portion of the heat shield 43 screwed to the tub 20 to extend heat transfer path, thereby preventing the tub from being influenced by the heat of the drying duct 40.

In addition, since the drying duct 40 is fixed to the outer circumferential surface of the tub 20 interposing the heat shield 43 therebetween, there is no need of installing a gasket on a connection portion between the drying duct 40 and the tub 20. That is, since the drying duct 40 is fixed to the tub 20, the drying duct 40 can shake or vibrate together with the shaking or vibrating tub 20.

Of course, it will be apparent to those skilled in the art that a sealing member may be installed at the connection portion between the drying duct 40 and the tub 20 so as to prevent the heat generated by the drying duct 40 from being leaked.

Meanwhile, since the condensation duct 50 is also directly fixed to the rear surface of the tub 20, there is no need of installing a gasket on a connection portion between the condensation duct 50 and the tub 20.

Hereinafter, drying cycle of the aforementioned drum type washing machine with drying function will be described.

As the drying cycle of the drum type washing machine starts, a power is applied to the heater 41 of the blower fan 42 to operate the blower fan 42 and the heater 41, so that hot air is generated.

The hot air generated in the drying duct 40 sequentially passes through the hot air inlet 20 a formed at the front surface of the tub 20 and the hot air passing holes 30 a formed at the front surface of the drum 30 and is then introduced into the inside of the drum 30.

At this time, the hot air passing holes 30 a are formed having a maximum sectional area of the air passage throughout the whole front surface of the drum 30 without lowering its strength. To this end, although the drum 30 rotates, the hot air passing holes are always positioned corresponding to the hot air inlet 20 a.

Therefore, the hot air introduced into the inside of the tub 20 through the hot air inlet 20 a is directly introduced into the inside of the drum 30 without bypassing another path.

Thereafter, the hot air introduced into the inside of the drum 30 progresses toward the hot air outlet 20 b formed in the diagonal direction of the hot air inlet 20 a to absorb moisture contained in the laundry and dry the laundry.

At this time, since the drum 30 rotates at a low speed to agitate the laundry such that the laundry is uniformly exposed to the hot air, thereby enhancing the drying efficiency.

Also, it is possible to sufficiently increase contact time between the hot air introduced into the inside of the drum 30 and the laundry by rotating the drum 30 at the low speed to tumble the laundry and then increasing the speed of the drum 30 to such a degree that the laundry is separated from the inner surface of the drum 30.

Meanwhile, after the drying is completed, the temperature of the hot air is decreased and is then discharged to the condensation duct 50 in a state that the discharge air absorbs moisture. Since the condensation duct 50 is connected to the rear lower portion of the tub 20, which is diagonally aligned with the front upper portion of the tub 20 that is the inflow direction of the hot air into the drum 30, the air of the drum 30 can be more smoothly discharged to the condensation duct 50.

In other words, since the air positioned at the hot air inlet 20 a of the front side of the tub 20 is light and warm but the air positioned at the hot air outlet 20 b of the rear side of the tub 20 is heavy and cold, the inventive air passage structure that the hot air inlet 20 a is formed at the front upper portion of the tub 20 and the hot air outlet 20 b is formed at the rear lower portion of the tub 20 is matched with the circulation principle of air by natural convection when considering the air circulation structure.

Also, since in the drum type washing machine of the present invention, the hot air penetrates the drum completely and is then discharged, the hot air can uniformly reach even the laundry positioned at a deep place of the drum 30, thereby enhancing the drying efficiency.

In the case of the wet air that is discharged from the hot air outlet 20 b and is then introduced into the condensation duct 50, the water feeder 51 feeds cold condensation water to the condensation duct 50, so that the cold condensation water flowing through the condensation duct 50 can remove the moisture contained in the wet air discharged to the condensation duct 50 using its condensation operation.

The dry air from which the moisture is removed by the condensation duct 50 is introduced into the drying duct 40 by the blower fan 42 built in the drying duct 40, is heated by the heater 41 built in the drying duct 40, and is then again introduced into the inside of the drum 30 by the blowing force of the blower fan 42.

By repeating the aforementioned operations, the laundry is dried.

Meanwhile, although the plate-screwing hole 431 for the screwing between the heat shield 43 and the tub 20 is formed at the embossing portion 43 b of the heat shield 43 together as shown in FIGS. 3 through 5, a modification, i.e., different structure, can be made.

In other words, as shown in FIG. 6, the heat shield 43 includes a base portion 430 a being closely in contact with the tub 20, and an embossing portion 430 b spaced apart from an outer surface of the tub 20 by a predetermined interval, to which the drying duct 40 is fixed, wherein a plate-screwing hole 431 for screwing the heat shield 43 to the tub 20 is formed at the base portion 430 a and a duct-screwing hole 432 for screwing the drying duct 40 to the heat shield 43 is formed at the embossing portion 430 b of the heat shield 43.

In the embodiment of FIG. 6, a coupling boss (see 200 of FIG. 5) protruded toward an outer circumferential surface of the tub 20 may be formed as a screwing portion corresponding to the plate-screwing hole 431 of the heat shield 43.

In addition, an embossing portion 430 c may be formed around the plate-screwing hole 431 formed at the base portion 430 a of the heat shield 43, for making it easy to determine an assembling position between the heat shield 43 and the coupling boss formed at the tub 20. The embossing portion 430 c is formed spaced apart from the embossing portion 430 b where the duct-screwing hole 432 for screwing the drying duct 40 to the heat shield 43 is formed.

As described above, the drum type washing machine with laundry drying function according to the present invention provides the following effects.

First, when the improved system of the present invention is applied to, since the air fed to the inside of the drum penetrates deep into the inside of the drum, the laundry can be uniformly dried, thereby enhancing the drying efficiency and the drying performance.

That is, the hot air generated in the drying duct is introduced into the front upper portion of the drum, flows in a diagonal direction, and is then discharged through the rear lower portion of the drum. Accordingly, the hot air is fed deep into the inside of the drum, so that the drying efficiency and the drying performance are enhanced.

Secondly, since the drying duct is connected to the tub unlike in the related art drum type washing machine with laundry drying function, the gasket can be prevented from being worn or torn.

Thirdly, since the drying duct is connected to the tub and thus the upper side of the gasket is exactly symmetric to the lower side of the gasket, it becomes possible to uniformly absorb vibration of the tub.

Fourthly, since hot air is introduced into the drum through the tub not via the gasket, it can be solved that the door is unnecessarily heated.

Fifthly, since the drying duct and the condensing duct are fixed to the tub, there is no need of installing a separate gasket at a connection portion between the drying duct and the tub, thereby shortening the airflow passage of each duct.

Sixthly, since the drying duct plays a role as a counterweight, the balancing capability is enhanced.

Seventhly, since the hot air passing holes are formed in an effective configuration at the front side of the drum, the flow of the hot air introduced into the drum can be maximized while maintaining the strength of the drum.

Lastly, since the drying duct is not directly coupled to the plastic tub but is indirectly coupled to the embossing portion of the heat shield screwed to the tub to extend heat transfer path, thereby preventing the tub from being influenced by the heat of the drying duct.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 

1. A washing machine with a laundry drying function, comprising: a cylindrical plastic tub having a hot air inlet formed at a front upper portion thereof and a hot air outlet formed at a rear lower portion thereof; a drum rotatably installed inside the tub; a drying duct provided with a heater and a blower fan that are mounted on an air passage of the drying duct and fixed to an upper predetermined portion of an outer circumference of the tub; a condensation duct for removing moisture contained in hot air exhausted through the hot air outlet of the tub; and a heat shield interposed between the tub and the drying duct, for shielding heat of the drying duct from being transferred directly to the tub.
 2. The washing machine of claim 1, wherein the heat shield is made of a metal material.
 3. The washing machine of claim 2, wherein the heat shield is made of an iron plate.
 4. The washing machine of claim 1, wherein the heat shield is made of a plastic material having a good heat-resistant property.
 5. The washing machine of claim 2, wherein the heat shield comprises an embossing portion spaced apart from an outer surface of the tub by a predetermined distance, to which the drying duct is fixed.
 6. The washing machine of claim 2, wherein the heat shield comprises: a base portion being closely in contact with the tub; and an embossing portion spaced apart from an outer surface of the tub by a predetermined interval, to which the drying duct is fixed, wherein the base portion has a plate-screwing hole for screwing the heat shield to the tub, and the embossing portion has a duct-screwing hole for screwing the drying duct to the heat shield.
 7. The washing machine of claim 6, wherein the tub comprises a coupling portion corresponding to the plate-screwing hole of the heat shield.
 8. The washing machine of claim 7, wherein the coupling portion is a coupling boss protruded from an outer circumferential surface of the tub.
 9. The washing machine of claim 2, wherein the heat shield comprises an embossing portion formed around a plate-screwing hole formed at a base portion of the heat shield, for making it easy to determine an assembling position between the heat shield and a coupling boss formed at the tub.
 10. The washing machine of claim 2, wherein the heat shield comprises: a base portion being closely in contact with the tub; and an embossing portion spaced apart from an outer surface of the tub by a predetermined interval, to which the drying duct is fixed, wherein the embossing portion includes a plate-screwing hole formed at both end portions of the embossing portion, for screwing the heat shield to the tub, and a duct-screwing hole formed at a center portion of the embossing portion, for screwing the drying duct to the heat shield.
 11. The washing machine of claim 10, wherein the embossing portion comprises a plurality of embossing portions arranged in the form of a band, two of the plurality of embossing portions being formed at a position facing each other in a circumferential direction, and the other(s) being formed at a position spaced apart from the two embossing portions by a predetermined distance in an axial direction of the tub.
 12. The washing machine of claim 11, wherein the duct-screwing holes formed at the respective center portions of the two embossing portions facing each other are formed at different positions.
 13. The washing machine of claim 10 or 11, wherein the tub comprises a coupling portion corresponding to the plate-screwing hole of the heat shield.
 14. The washing machine of claim 13, wherein the coupling portion is a coupling boss protruded from an outer circumferential surface of the tub.
 15. The washing machine of claim 10, wherein the heat shield further comprises a two-stage embossing portion which is twice embossed and formed around the plate-screwing hole formed at the embossing portion of the heat shield, for making it easy to determine an assembling position between the heat shield and a coupling boss formed at the tub.
 16. The washing machine of claim 10, wherein the drying duct has a screwing piece for screwing the drying duct to the heat shield.
 17. The washing machine of claim 16, wherein the screwing piece has a length protruded downward than a lower surface of the drying duct.
 18. The washing machine of claim 1, wherein the heat shield has an area covering a transferable range of radiant heat from the heater.
 19. The washing machine of claim 16, wherein the heat shield is a plate having a similar curvature to the tub.
 20. A washing machine with a laundry drying function, comprising: a cylindrical plastic tub having a hot air inlet formed at a front upper portion thereof and a hot air outlet formed at a rear lower portion thereof; a drum rotatably installed inside the tub and having a hot air passing hole formed at a predetermined portion of a front thereof, for allowing hot air that has passed through the hot air inlet of the tub to be introduced into an inside of the drum; a drying duct provided with a heater and a blower fan that are mounted on an inner air passage of the drying duct such that hot air is generated and fixed to an upper predetermined portion of an outer circumference of the tub; a condensation duct for removing moisture contained in hot air exhausted through the hot air outlet of the tub; and a heat shield interposed between the tub and the drying duct, for shielding heat of the drying duct from being transferred directly to the tub, wherein the heat shield is made of steel, comprises a base portion being closely in contact with the tub and an embossing portion spaced apart from an outer surface of the tub by a predetermined interval, to which the drying duct is fixed, the embossing portion including a plate-screwing hole formed at both end portions of the embossing portion, for screwing the heat shield to the tub, and a duct-screwing hole formed at a center portion of the embossing portion, for screwing the drying duct to the heat shield. 